I prefer invoking Cthulhu. But, you must have quality chicken entrails to drape over your monitor.
Edit: To the O.P.: Lest you think we're being unduly snarky, advertising that works is hard to find and highly peculiar to the specific item or book being advertised. No one knows at first what will work, or if anything at all will work.
Edited by: Joseph M Erhardt on Dec 28, 2017 6:03 PM
Joseph is right. The useful online advertisers are few and far between, and becoming more difficult to get selected as time goes by. I'm running an ad tomorrow with new site to me. I'd like to say I'm excited about the prospects, but I'm expecting comedic relief more than sales.
It costs very little to find out whether your advertising is working or not. You can quit at just a couple of dollars if you're not selling any books - but you'd be much better off holding out for a bit, and then tweaking, changing, learning, and trying different things. Some people do paid advertising on Facebook, but my experience is that it just sucks up my money. People click too much on Facebook with no intent to buy. On Amazon people are there BECAUSE they're usually looking for books to buy. Some people are very savvy with FB and do well, but I think you have to really know your stuff. I'd stay away.
You can do tons and tons of free advertising in book groups on Facebook. It's a bit time consuming, but the time investment has paid off for me. What you basically have to do is join a ton of book groups, and then get a little involved and post your book on their pages a couple of times a week. Google can give you lots of pointers on doing that.
That's what I've been doing so far, anyhow. I think thems there are the basics. Anything else is a bit more complicated and costly - though I'm about to look into Bookbub and Goodreads advertising. I thought Bookbub only did book deals, but after submitting for one and not getting it, I got an email invite telling me I've been approved to advertise with them. I don't see anything about that on their website, so I have to check the email again to see what's up.